MTV is going through a generational shift and a slimming of its senior exec hierarchy.

Brian Graden, prexy of MTV Networks Music Group and prexy of the Logo cabler, will depart the company at the end of this year when his contract expires. Graden oversees programming for MTV, VH1, CMT and Logo. He’s been the key player shaping programming for MTV and VH1 for more than 10 years.

But MTV Networks said Graden’s post will not be filled. It’s a tacit acknowledgement that the Viacom cablers have long been top-heavy with execs. At a time when cost-cutting is a mantra throughout Viacom and every other major media concern, it’s no surprise that MTV Networks will simply eliminate a layer of management with Graden’s departure.

No further changes are planned inside the MTV Networks structure, according to MTV Networks prexy Van Toffler. MTV’s Tony DiSanto, VH1’s Jeff Olde, CMT’s Bob Kusbit and Logo’s Dave Mace will continue to head up original programming at their respective channels; a specific change in the reporting structure has not yet been determined.

Graden may also not be straying too far from the MTV Networks. MTV is in talks with Graden about setting up a production deal at the Viacom-owned cabler.

“We’re in the throes of discussing a continuing relationship,” Toffler said. “I hope we continue to get his twisted, creative bent on TV and long- and short-form content.”

Graden leaves as MTV once again goes through a big generational shift — this time reinventing itself as a channel for the so-called “millennial” audience.

Graden, DiSanto and that channel’s team is currently rolling out an MTV makeover and adjusting its target to auds born in the late 1980s and early 1990s. That audience, coming of age during the Obama administration, is said to be more optimistic and looking for more aspirational programming, according to Toffler.

“MTV sheds its skin as a new generation comes in and takes over, and we’re now reinventing MTV for millenials,” Toffler said. “Brian will stick around to help with the transition, and we’ve just launched a whole bunch of shows under our new filter… (but) this is a wonderfully organic time for him (to depart).”

Those skeins launched on Monday, the same day Graden announced his exit: “It’s On with Alexa Chung,” a new Internet-savvy talk/variety show, and “DJ and the Fro,” among others.

“I’ve worked with Tony a lot this past year to put together this brand evolution,” Graden said.

With the MTV changes in place, and the four-year-old Logo now well-established, Graden said he felt the time was right to focus on other pursuits.

Graden had been toying with his next move for a while, having spent 12 years at the conglom. The exec said he started mulling his end game five years ago, during his last contractual renegotiation with MTV Networks parent Viacom. According to the New York Post, Graden makes as much as $7 million a year.

Without commenting on that number, Graden said he has been “treated exceedingly well,” and that he now has the flexibility to pursue things – such as writing – “that might not ever pay me a dime.”

Graden said he’s been spending much of his free time writing music; the musical he’s been penning just received its second staging in Los Angeles last week. He also hopes to write books, including one on cultural phenomenon.

As for that potential return to producing, Graden said he’s kicking around different ways to do TV – and is inspired by the mini-studio that Tyler Perry has created.

“I want to shape something unique,” he said. “I’m blessed to have this flexibility.”

Graden first joined MTV in July 1997 as exec VP of programming. He added VH1 stripes in 2002 and helped launch Logo in 2005.

There’s a touch of irony in Graden’s passion for music (for years he would send mix CDs to friends and colleagues for the holidays): During his tenure, Graden oversaw MTV and VH1’s move away from music and more toward lifestyle series and reality skeins.

At MTV, Graden brought on hit series such as “The Osbournes,” “TRL,” “Pimp My Ride,” “Jackass” and “Laguna Beach.” He also expanded the net’s “Fight for Your Rights” public service campaigns. And he launched Logo as president of that channel, geared toward gay, lesbian, transsexual and bisexual auds.

“Everything from reality to live daily programming to scripted series to comedy to drama, as well as really unforgettable pro-social events, he really dimensionalized the brand to do more than just music and music videos,” Toffler said.

Prior to MTV, Graden ran the Foxlab programming unit within Fox. And he famously was also instrumental in the launch of “South Park,” which originated as a Christmas video that Graden commissioned from Matt Stone and Trey Parker.